As computers and Internet technologies have advanced in these years, individuals have been able to easily send information (contents), and the amount of contents available for users have been rapidly increasing.
Although the amount of contents have been rapidly increasing and they can be freely used, there are many low-quality contents.
Therefore, it may be a good idea to evaluate the quality of contents and provide the result for the users. It is, however, very time-consuming for people to view and evaluate a huge amount of contents. In addition, person's evaluation depends on the evaluator's preference.